diff --git a/.travis-ocaml.sh b/.travis-ocaml.sh
index 52d70cb..19f7dd1 100644
--- a/.travis-ocaml.sh
+++ b/.travis-ocaml.sh
@@ -14,23 +14,32 @@ full_apt_version () {
 
 set -uex
 
+
+# the ocaml version to test
+OCAML_VERSION=${OCAML_VERSION:-latest}
+OPAM_VERSION=${OPAM_VERSION:-2.0.0}
+OPAM_INIT=${OPAM_INIT:-true}
+
 if [ "${INSTALL_LOCAL+x}" = x ] ; then
   if [ "$TRAVIS_OS_NAME" = osx ] ; then
     echo INSTALL_LOCAL not permitted for macOS targets
     exit 1
   fi
 
-  if [ "${OPAM_SWITCH:=system}" != system ] ; then
-    echo "INSTALL_LOCAL requires OPAM_SWITCH=system (or unset/null)"
-    exit 1
-  fi
+  case ${OPAM_VERSION} in
+      2.0.0)
+          if [ "${OPAM_SWITCH:=ocaml-system}" != ocaml-system ] ; then
+              echo "INSTALL_LOCAL requires OPAM_SWITCH=ocaml-system (or unset/null)"
+              exit 1
+          fi ;;
+      *)
+          if [ "${OPAM_SWITCH:=system}" != system ] ; then
+              echo "INSTALL_LOCAL requires OPAM_SWITCH=system (or unset/null)"
+              exit 1
+          fi ;;
+  esac
 fi
 
-# the ocaml version to test
-OCAML_VERSION=${OCAML_VERSION:-latest}
-OPAM_VERSION=${OPAM_VERSION:-2.0.0}
-OPAM_INIT=${OPAM_INIT:-true}
-
 # the base opam repository to use for bootstrapping and catch-all namespace
 case $OPAM_VERSION in
     2.0.0) BASE_REMOTE=${BASE_REMOTE:-git://github.com/ocaml/opam-repository#2.0.0} ;;
@@ -81,6 +90,13 @@ install_ppa () {
   fi
 }
 
+install_ocaml () {
+    sudo apt-get install -y  \
+         ocaml ocaml-base ocaml-native-compilers ocaml-compiler-libs \
+         ocaml-interp ocaml-base-nox ocaml-nox \
+         camlp4 camlp4-extra
+}
+
 install_on_linux () {
   case "$OCAML_VERSION,$OPAM_VERSION" in
     3.12,1.2.2)
@@ -106,6 +122,7 @@ install_on_linux () {
     4.01,2.0.0)
         OCAML_FULL_VERSION=4.01.0
         OPAM_SWITCH=${OPAM_SWITCH:-ocaml-system}
+        install_ocaml ;
         install_opam2 ;;
     4.02,1.1.2)
         OCAML_FULL_VERSION=4.02.3
@@ -234,7 +251,8 @@ install_on_osx () {
     4.06,2.0.0) OCAML_FULL_VERSION=4.06.1; install_opam2 ;;
     4.07,1.2.2) OCAML_FULL_VERSION=4.07.0;
                 OPAM_SWITCH=${OPAM_SWITCH:-system};
-                brew install ocaml; brew install opam ;;
+                brew install ocaml;
+                brew install opam ;;
     4.07,2.0.0) OCAML_FULL_VERSION=4.07.0;
                 OPAM_SWITCH=${OPAM_SWITCH:-ocaml-system};
                 brew install ocaml;
diff --git a/src/ci_opam.ml b/src/ci_opam.ml
index c554fbe..3a702bb 100644
--- a/src/ci_opam.ml
+++ b/src/ci_opam.ml
@@ -229,7 +229,7 @@ let lint_pins pkg pins =
 ;; (* Go go go *)
 
 with_fold "Prepare" (fun () ->
-    set "-ue";
+    set "-uex";
     unset "TESTS";
     export "OPAMYES" "1";
     ?| "eval $(opam config env)";
@@ -261,6 +261,7 @@ with_fold "Prepare" (fun () ->
         | _   -> ?|~ "opam lint %s" opam);
     let pins = lint_pins pkg pins in
     List.iter pin pins;
+    ?|~ "echo %s are pinned" (String.concat ", " (List.map fst pins));
     ?|  "eval $(opam config env)";
     ?|  "opam install depext";
     (* Install the external dependencies *)